Limited SNR adjustment using DGTeam

[#1]

My SNR had gone up to 15dB so I tried to decrease it using DGTeam firmware but the lowest I can force it down to is about 10dB. 
Is there any 21CN related restriction that prevents firmware like DGTeam, DMT, and Routerstats making significant adjustments to SNR?
Thanks
Martin

[#2]

The maximum tweak downwards that you can make to your SNR with the dgteam GUI is to set it to 1.  This will lower the SNR by about 5.5dB, which is what you are seeing.  There is a trick to force it lower by using negative numbers, but you can only do this from the telnet interface.
Have a look at http://www.kitz.co.uk/routers/dg834GT_targetsnr.htm which has instructions.
It's also worth trying to find out why your target margin has been pushed up to 15dB implying that there's instability or lots of errors on your line.

[#3]

Hi Robr,
Thanks for that.  I had assumed that 1% was 1% of SNR and not 1% of 5dB.  That is useful to know and now I understand why some people are requesting the ability to request -ve adjustment values in DGTeam.
The reason my SNR is so high is that I was experimenting with a different modem 1 month ago and kept power cycling not realising it would make BT think I had a connection problem.  I keep asking PlusNet if they can get my SNR lowered but am not getting far.  After my repeated power cycling it went up to 34dB but a few weeks ago it dropped to 15dB but no lower
Thanks
Martin